In this Feb. 1 photo, a United Airline jet prepares to land at Cleveland Hopkins International Airport. / John Kuntz, AP

by Bart Jansen and Laurie Cipriano , USA TODAY

by Bart Jansen and Laurie Cipriano , USA TODAY

Federal investigators are reviewing a United Airlines flight that encountered severe turbulence Monday that injured five people, including one passenger who called it the scariest 25 seconds of her life.

The Federal Aviation Administration is investigating United Flight 1676 from Denver to Billings, Mont. The National Transportation Safety Board is gathering information about the incident, which happened around noon Monday while the jet was at 34,000 feet in northern Wyoming.

Three flight attendants and two passengers were taken to the hospital after the jet landed in Billings, and one attendant remained hospitalized Tuesday.

"We are providing her support, and a United supervisor is by her side at the hospital," said Christen David, a United spokeswoman. "Our flight safety investigators are working closely with the NTSB to analyze the flight data."

One passenger, Kerri Mullins of Arvada, Colo., had just taken a picture of clear blue skies when the jet suddenly turned sharply to the right and plunged.

"It's the most helpless feeling ever - to just be sitting there and not have any control over anything," said Mullins, who called it the scariest 25 seconds of her life. "Everything flew out of everybody's hands."

Though fatal accidents have almost disappeared from commercial flights, air safety experts warn that wind turbulence can bounce a plane dozens of feet while landing or taking off â?? and hundreds of feet while cruising.

About a dozen people each year suffer serious injuries because of turbulence, typically requiring a trip to the hospital, according to reports to the NTSB. Dozens more suffer minor injuries each year.

The NTSB reports describe passengers breaking ankles or fracturing ribs while dashing to the lavatory or simply leaving a seat belt unfastened. Flight attendants are hurt even more often and often worse when thrown across the cabin like dolls or slammed by beverage carts.

Although thunderstorms are obvious hazards to avoid, turbulence can occur in clear air through wind shear â?? when wind changes speed or direction, either vertically or horizontally â?? or through buoyant changes of air rising and falling like in a thunderstorm.

Pilots relay warnings about rough patches, but the FAA said there weren't any reports Monday where the United flight ran into trouble. That's why safety experts stress the importance of wearing seat belts even in clear weather.

"People that did not have their seat belts on had flown out of their seats and hit the ceiling," Mullins said. After the jet stabilized, she said, passengers had to hand back cellphones and wallets that flew around the cabin.

Another United passenger, Bill Dahlin, told KTVQ in Billings that one woman hit the ceiling so hard that the panel above her cracked, and another woman cried out for her baby.

"I have flown a lot, and I do know you run into things like this," said Dahlin, who wasn't injured. "This happened to be a lot rougher than what I'm accustomed to."

Contributing: John Bacon and Melanie Eversley. Laurie Cipriano reports for KUSA-TV in Denver.